Heretofore, a temperature control device has been used in conjunction with a stack of fuel cells. The conventional device is of the type in which heat medium is circulated during operation and which is inserted between adjacent ones of stacked fuel cells to effect heating at start-up of the fuel cells to promote the reaction and to take out heat produced during normal operation of the fuel cells.
FIG. 1 shows a structure of a typical conventional temperature control device. In FIG. 1, numerals 1 and 3 denote temperature control plates having reaction gas passage ducts 2 and 4 on surfaces opposite to the confronting surfaces. A heat exchanger piping 5 is mounted between these temperature control plates 1 and 3. The piping 5 has an inlet and outlet that are connected to a pump 6 by a connection piping 5a externally of the temperature control plates 1 and 3, pump 6 being adapted in turn to supply cold or warm water to the piping 5.
In operation, at start-up of the fuel cells, warm water is supplied by pump 6 to the heat exchanger piping 5 to promote the reaction to effect heat transfer to the temperature control plates so as to heat the stack of fuel cells above and below the temperature control plates. During normal operation of the fuel cells, the heat generated in the fuel cells must be removed for preventing fuel cell destruction due to rises in temperature. The heat generated in the fuel cells is transferred to the temperature control plates 1 and 3 from above and below, and thence to the heat exchanger piping 5 sandwiched between the plates 1 and 3. At this time, cold water is supplied to the piping 5 by the pump 6 which has been switched to a conduit different from that used for start-up of the fuel cells. Thus, evolved heat is transferred to the cold water and taken out, at the temperature control plates 1 and 3.
It is seen from the above that drive means such as pump 6 is required in the conventional temperature control device for circulation of cold or warm water. The prior-art device is therefore in need of a motive power for operation of these drive means. In addition, the operation of the prior-art device may not be completely reliable because the drive means consists of a pump or a motor having movable parts.